Stratification resistant emulsions

ABSTRACT

Emulsions containing a hydrocarbon liquid in a continuous phase and alcohol and/or water in a dispersed phase are provided. The emulsions are stabilized by an emulsifier and a coupling agent. The emulsifier is a copolymer containing at least one relatively hydrophobic polymeric block of styrene or a ring substituted styrene monomer, and at least one relatively hydrophilic polymeric block of at least one monomer, such as ethylene oxide, selected from the group having the formula H(O—R) n OH, where R is an aliphatic radical containing from 1 to 4 carbon atoms and n is a number between 20 and 300. The coupling agent is a copolymer containing at least one polymeric block of styrene or ring substituted styrene monomer, and at least one block being of a saturated or unsaturated aliphatic hydrocarbon moiety, such as butadiene. The emulsifier is present in an amount sufficient to form micelles of the relatively hydrophilic polymer block sufficient to contain the dispersed phase and the coupling agent is present in an amount that is sufficient to substantially prevent the dispersed phase droplets from coalescing while not being present in a sufficiently high amount that micelles of the styrene containing polymeric blocks of the coupling agent form in the continuous phase of the emulsion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage entry under 35 U.S.C. § 371 ofPCT/AU98/00614, filed Aug. 5, 1998.

TECHNICAL FIELD

The present invention relates to emulsions containing alcohol and/orwater in a dispersed phase and a hydrocarbon liquid in the continuousphase. More particularly the present invention relates to such emulsionsthat are resistant to stratification on relatively long term undisturbedstorage at ambient temperature.

BACKGROUND ART

It is known from the applicant's Australian patent specification 544.728that emulsions containing alcohol and/or water in one phase and ahydrocarbon liquid in the other may be formed using an emulsifier thatis a block copolymer of ethylene oxide and styrene type monomers. Theseemulsions are of particular utility as liquid transport fuel in whichhydrated methanol or hydrated ethanol is dispersed in diesel oil orgasoline. Hydrated alcohol in diesel oil (termed AW/D) emulsionsrepresent a new and potentially cost effective option for significantlyreducing particulate and NOx emissions from diesel engines. Emulsions ofhydrated alcohol in gasoline exhibit reduced vapour pressure, increasedwater tolerance and reduced NOx emission on combustion as compared withanhydrous alcohol solutions in gasoline. When the alcohol is ethanolproduced from biomass there can be a reduction in the net emission ofcarbon dioxide (“greenhouse gas”) as compared with the use of unblendedpetroleum fuel.

The arrangement described in the above mentioned specification utilisednot only a block copolymer as the emulsifier but also a block copolymeras a coupling agent. The coupling agent typically comprised a blockcopolymer of butadiene and styrene type monomers and was described ascontaining butadiene and styrene in weight ratios of at least 2:1,preferably at least 3:1. The emulsifier and the coupling agent aredescribed in that specification as being present in the emulsion in aratio of from 1:3 to 3:1. In these ratios solutions of the twocopolymers are compatible.

It has been found that while the AW/D emulsions described in theaforementioned Australian patent specification produce generally stableemulsions they do suffer from a problem of stratification, i.e., atendency for the dispersed or discontinuous phase droplets to rise ifthey are less dense than the continuous phase of the emulsion, called‘creaming’, or to fall if they are more dense than the continuous phase,called ‘settling’. While this stratification may take a relatively longtime and may be readily reversed by gentle agitation it is a majorcommercial disadvantage as there is the possibility that any givenaliquot of emulsion may, after a period of relatively long-termundisturbed storage, contain more or less of the dispersed phasecomponent than is intended. In the case of an emulsion used as a fuelsuch stratification makes the starting and/or running of an enginedifficult, if not impossible.

DISCLOSURE OF INVENTION

The present invention relates to emulsions containing in a continuousphase a hydrocarbon liquid and in a dispersed phase alcohol and/or waterin the presence of:

(a) an emulsifier being a copolymer containing at least one relativelyhydrophobic polymeric block of at least one monomer selected from thegroup comprising styrene and ring substituted styrenes, and at least onerelatively hydrophilic polymeric block of at least one monomer selectedfrom the group having the formula H(O—R)_(n) OH where R is an aliphaticradical containing from 1 to 4 carbon atoms and n is a number between 20and 300, and

(b) a coupling agent being a copolymer containing at least one polymericblock of at least one monomer selected from the group comprising styreneand ring substituted styrenes, and at least one block being a saturatedor unsaturated aliphatic hydrocarbon moiety, the emulsifier beingpresent in an amount sufficient to form micelles of the relativelyhydrophilic polymer block sufficient to contain the dispersed phase andthe coupling agent being present in an amount that is sufficient tosubstantially prevent the dispersed phase droplets from coalescing whilenot being present in a sufficiently high amount that micelles of thestyrene containing polymeric blocks of the coupling agent form in thecontinuous phase of the emulsion.

The absolute amounts of the emulsifier and the coupling agent can bedetermined for any given emulsifier and coupling agent by quantitativetesting. It is apparent to the present inventor that the amount of thecoupling agent in the emulsion is important and typically approaches thesolubility limit of the coupling agent in the continuous phase. If theamount of the coupling agent is lower than the critical amount it willnot couple effectively with the micelles of the emulsifier and thereforestratification of the dispersed phase of the emulsion will not beinhibited. If the amount of the coupling agent is higher than thecritical amount it will form micelles of the styrene containingpolymeric blocks of the coupling agent which will in turn causeflocculation of the dispersed phase to occur. The solubility of thecoupling agent in the continuous phase can be adjusted by an alterationof the amount of the styrene moiety relative to the hydrocarbon moietyin the coupling agent. The solubility will also depend to some extentupon the aromaticity of the hydrocarbon liquid comprising the continuousphase. The more aromatic is the hydrocarbon liquid the higher will bethe solubility of any given coupling agent.

The maximum amount of emulsifier is not as critical as the maximumamount of the coupling agent as, within reasonable limits, the presenceof an excess of emulsifier has only an economic disadvantage and not atechnical one. The emulsifier should be present in an amount greaterthan 3 times the amount of the coupling agent as is described in moredetail later in this specification. Preferred amounts of the couplingagent in the emulsion are in the range of from 0.75 to 1.5 gm/l. Whenthe dispersed phase is hydrated methanol it is preferred that thecoupling agent is present in the emulsion in the range of from 0.75 to1.0 gm/l whereas in the case of the dispersed phase comprising hydratedethanol the preferred range is from 1.0 to 1.5 gm/l.

In total the copolymer content of the emulsion, i.e. the combined amountof the emulsifier and of the coupling agent, is preferably in the rangeof from 4 to 10 gm/l. In the case of emulsions containing hydratedmethanol in an amount of 12% by volume in the dispersed phase thepreferred amount of copolymers is 4 to 6 gm/l, more preferably 5 gm/l,and in the case of emulsions containing hydrated ethanol in an amount of15% by volume in the dispersed phase the preferred concentration ofcopolymers is 5 to 8 gm/l, more preferably 6 gm/l. In the case ofemulsions that contain greater amounts of alcohol and/or water in thedispersed phase the preferred amount of the copolymers will typicallyremain less than 10 gm/l, however in this case the ratio of theemulsifier to the coupling agent will rise. This is because, as theamount of the dispersed phase increases so the quantity of emulsifierrequired increases in proportion to the increase in the surface area ofthe dispersed phase of the emulsion; by contrast, the quantity ofcoupling agent stays substantially constant as the amount of thedispersed phase increases.

As used in this specification the following terms have the meaningsindicated:

Alcohol: This term means methanol or ethanol or mixtures thereof andHydrocarbon liquid: This term includes all liquid fractions obtainedfrom petroleum crude oil and synthetic liquid hydrocarbons obtained fromthe processing of gaseous or solid hydrocarbons.

The hydrocarbon liquid is preferably selected from the group comprisinggasolines, kerosenes, diesel oils, gas oils and fuel oils. The gasolinesare liquid hydrocarbons boiling below 190° C. The kerosenes, diesel oilsand gas oils boil between 170° and 480° C., while the fuel oils boilabove 450° C.

The hydrocarbon liquid is preferably selected from the gasolines, thekerosenes which boil between 170 and 230° C., the diesel oils which boilfrom 170 to 315° C. and the gas oils that boil from 315 to 480° C. Theinvention is particularly applicable to the high boiling pointkerosenes, the diesel oils and the low boiling point gas oils when thedispersed phase comprises a hydrated alcohol. In the case where thedispersed phase comprises only water the preferred hydrocarbon liquid isselected from the diesel oils, the gas oils, the fuel oils and thehydrocarbon liquids boiling above 480° C.

The dispersed phase of the emulsions preferably comprises a hydratedalcohol, which preferably contains from 0.1 to 10% by volume of water.The dispersed phase is preferably methanol or ethanol, or mixturesthereof, together with water.

The proportions of alcohol and/or water to hydrocarbon liquid may varyover wide limits. For alcohol containing emulsions, a hydrated alcoholcontent of between 10 and 30% by volume is preferred.

The emulsifier is preferably a copolymer containing at least onepolymeric block of at least one monomer selected from the groupcomprising styrene and ring substituted styrenes and at least onepolymeric block of at least one monomer selected from the group havingthe formula H(O—R)_(n) OH, where R is an aliphatic bivalent hydrocarbonradical containing from 1 to 4 carbon atoms and n is a number between 20and 300, more preferably between 22 and 130. The emulsifier ispreferably a pure di-block copolymer or a reaction mixture containingprincipally di-block copolymer and tri-block copolymer having two blocksof the styrene monomer, together with some unreacted homopolymer of theH(O—R)_(n) OH monomer.

In a particularly preferred embodiment of the present invention theemulsifier is a polyethylene oxide-polystyrene copolymer. Thepolyethylene oxide block is preferably formed first with a molecularweight of between 1,000 and 10,000. The polyethylene oxide and thepolystyrene are preferably present in a weight ratio of 1 part ofpolyethylene oxide to from 0.8 to 1.5 parts of polystyrene, morepreferably from 1.0 to 1.25 parts of polystyrene. In preferredembodiments of the invention the emulsifier is produced by the reactionof styrene monomer with polyethylene oxide homopolymer in the presenceof a free radical initiator. The reaction product formed without chaintransfer agents, comprising polyethylene oxide-polystyrene di-blockcopolymer . . . polystyrene-polyethylene oxide-polystyrene tri-blockcopolymer, unreacted polyethylene oxide homopolymer and a minorproportion of various other higher molecular weight dimeric and trimericspecies and polystyrene homopolymer, is particularly suitable for use inthe present invention.

The coupling agent is preferably a copolymer containing at least onepolymeric block of at least one monomer selected from the groupcomprising styrene and ring substituted styrenes and at least onepolymeric block of at least one compound selected from the groupcomprising saturated or unsaturated aliphatic hydrocarbons, preferablybutadiene or isoprene. Alternatively the hydrocarbon may comprise asingle long chain hydrocarbon moiety rather than a polymer made up of aplurality of recurring monomeric entities. The coupling agent ispreferably a pure diblock copolymer or a tapered block copolymer. Suchcopolymers are preferably produced by anionic solution polymerisation asthis technique produces copolymers with a defined structure and a narrowmolecular weight distribution. It is preferred that the coupling agentcontains styrene and the aliphatic hydrocarbon in the weight ratio offrom 1:0.3 to 1:1, most preferably from 1:0.42 to 1:0.66. These ratiosare outside the range of at least 1:2 and most preferably 1:3 stated tobe desirable in Australian patent specification 544.728 and lead in anopposite direction from the teaching of that specification.

The coupling agent preferably has a molecular weight of from 13,000 to400,000, more preferably the 100,000 to 170,000, most preferably 120,000to 150,000. It is preferred that styrene comprises from 50 to 77% byweight of the coupling agent, most preferably 50 to 70% depending on thearomatic content of the continuous phase of the emulsion. It has beenfound that when the aromatic content of the continuous phase is lessthan 22% it is preferable for the styrene content of the coupling agentto be in the range of from 50 to 60% by weight. By contrast when thearomatic content of the continuous phase is more than 23% it ispreferable for the styrene content of the coupling agent to be in therange of from 60 to 70% by weight.

As has been previously described, at the preferred proportions ofstyrene the solubility of the coupling agent is limited in thecontinuous phase of the emulsion. This limited solubility encouragescoupling of the styrene moieties on the emulsifier with those of thecoupling agent thus preventing coalescence of the droplets in thedispersed phase of the emulsion.

It has surprisingly been found that the emulsifier and the couplingagent are desirably included in the emulsion in quite specific amounts.The emulsifier should preferably be present in such an amount that theemulsifier is able to form micelles of its relatively hydrophilicpolymer (typically polyethylene oxide) block(s) in a concentrationsufficient to contain the alcohol and/or water dispersed phase. Thecoupling agent should be present in an amount that enables it to couplewith, or to form polystyrene micelles only with, the styrene moieties onthe emulsifier and to thereby substantially prevent the dispersed phasedroplets from coalescing, while not being present in an amountsufficient to form polystyrene micelles of the styrene containingpolymeric blocks of the coupling agent itself in the continuous phase ofthe emulsion. This means that in preferred embodiments of the inventionthe emulsifier and the coupling agent will be present in a weight ratioof more than 3.0:1, preferably at least 3.5:1, and more preferably atleast 4:1. It is surprising that, at these preferred ratios, solutionsof the emulsifier and of the coupling agent are not compatible. Theseratios are outside the range of 1:3 to 3:1 stated to be desirable inAustralian patent specification 544.728 and lead in an oppositedirection from the teaching of that specification.

Without being limited to the theory it is suggested that the mechanismof the present emulsification is one of steric stabilisation. It isconsidered that the emulsifier will form hydrophilic (typicallypolyethylene oxide) micelles in the continuous phase of the emulsion.The alcohol and/or water is contained within these micelles, thequantity of the alcohol and/or water that can be accommodated in theemulsion is therefor dependent upon the concentration of these micellesin the emulsion. The styrene block or blocks of the emulsifier have alimited solubility in the continuous phase but will project into thecontinuous phase from the micelles as their solubility is higher in thecontinuous phase than in the discontinuous or dispersed phase.

The coupling agent has blocks of styrene containing polymer which areonly of limited solubility in the continuous phase and a hydrocarbonmoiety which is of much greater solubility in the continuous phase ofthe emulsion. It is believed that the styrene containing polymer blocksof the coupling agent will couple with the corresponding styrenecontaining polymer blocks of the emulsifier to form a zone of couplingagent surrounding each micelle: If, however, the amount of couplingagent is increased above a certain concentration, then, as has beendiscovered by the present inventor, in addition to coupling with theemulsifier the coupling agent molecules will couple with themselves toform polystyrene micelles. If this happens then rather than acting tomaintain a sub-micron dispersion of alcohol and/or water droplets thecoupling agent unexpectedly acts to flocculate the dispersed phase,forming comparatively large sized droplets. The presence of the couplingagent is however essential to the maintenance of the sub-micron sizedispersion of alcohol and/or water droplets. In the absence of thecoupling agent the micelles of emulsifier flocculate, as the styrenecontaining polymer blocks of the emulsifier in adjacent micelles coupletogether.

The dispersed phase droplets behave in accordance with Stokes Law andmay stratify in the emulsion in accordance with the number of droplets,the droplet diameter, the relative density of the dispersed andcontinuous phases of the emulsion and the viscosity of the continuousphase. The stratification, which is manifest either as creaming, wherethe dispersed phase rises in the continuous phase, or settling, wherethe dispersed phase sinks in the continuous phase, may be prevented, orat least reduced, by the establishment of a suitable sub-micron sizedistribution of the dispersed phase droplets.

It is believed that the emulsifier will form hydrophilic (typicallypolyethylene oxide) micelles in the continuous phase of the emulsionand, provided the concentration of these micelles is above the necessaryminimum concentration for the volume of alcohol and/or water to beincorporated into the emulsion, will contain the alcohol and/or waterinside the micelles to form the dispersed phase. It is believed thatthese initially formed dispersed phase droplets are of a sufficientlysmall size that they are not susceptible to stratification. It isfurther believed that if that these initially formed dispersed phasedroplets can be prevented from coalescing or agglomerating the emulsionwill remain resistant to stratification. If the coupling agent ispresent in a sufficient amount to couple with the styrene polymer blocksof the emulsifier, but without the formation of micelles of its own,then the initially formed dispersed phase droplets will be held apartand will not be able to couple with one another and coalesce thedispersed phase droplets. The micelles of the emulsifier will thus bestabilised by coupling agent molecules with their styrene polymer blockscoupled to the emulsifier and their hydrocarbon blocks solvated by thecontinuous phase of the emulsion.

While the correct selection of the emulsifier and the coupling agent andtheir relative amounts are important the present inventor has found thata preferred process of forming the emulsion is also desirable. Theemulsifier is preferably first dissolved in the alcohol and/or water. Inorder to induce dissolution of the emulsifier it may be necessary toadjust the reaction conditions used to form the emulsifier to render itmore hydrophilic and/or to use an aqueous solution of an alcohol todissolve the emulsifier. The coupling agent is preferably firstdissolved in the hydrocarbon liquid. The alcohol and/or water containingthe dissolved emulsifier is then added to the hydrocarbon liquidcontaining the dissolved coupling agent. It is preferred that thesolution of the coupling agent in the hydrocarbon liquid be subjected toagitation both before and after the addition of the alcohol and/or watercontaining the dissolved emulsifier.

The agitation of the components to the emulsion is preferably carriedout using static in-line mixers. In the case of the agitation followingthe addition of the alcohol and/or water containing the emulsifier tothe hydrocarbon liquid containing the dissolved coupling agent it isdesirable that the mixing be carried out with high shear. In preferredembodiments of the invention the agitation, combined with the selectedemulsifier and coupling agent, and the use of the process according tothe present invention produces emulsions with dispersed droplets havingdiameters in the range of from 0.1 to 2.0 microns, more preferably from0.1 to 0.9 microns with an average diameter of about 0.5 microns.

BRIEF DESCRIPTION OF DRAWINGS

The following description of a preferred embodiment of the presentinvention is provided as an example of the invention and is describedwith reference to the accompanying drawings in which:

FIG. 1 is a flow diagram for a blending facility for forming emulsionsaccording to the present invention, and

FIG. 2 is a graph showing the way in which the percentage stratificationof the dispersed phase of an AW/D emulsion changes as the weight ratioof emulsifier to coupling agent changes.

BEST MODE FOR CARRYING OUT THE INVENTION

(i) Production of Emulsifier

The following method was used for the production of a 3.27 tonne batchof an emulsifier which is a copolymer of polyethylene oxide and styrene.The method comprised the steps of:

a) A suitably sized reactor vessel which is compatible with theemulsifier was cleaned and dried

b) The following materials were charged into the reactor vessel:

Polyethylene oxide, molecular weight 1500  804.0 kg Xylene solvent1120.0 kg

The polyethylene oxide had been heated to 50-60° C. overnight and wasadded to the reactor vessel through the manhole.

c) Styrene monomer 804.0 kg

was charged into the reactor monomer feed headtank.

d) Tertiary butyl perbenzoate free radical initiator 116.2 kg Xylenesolvent 426.0 kg

where charged into the reactor catalyst feed headtank.

e) A gentle nitrogen flow through the reactor vessel was commenced andthe agitator speed set to 40 rpm. The reactor vessel was heated by theapplication of full heat to the jacket of the reactor vessel.

f) When the reactor vessel temperature had reached and levelled out at140° C. the styrene monomer from the reactor monomer feed headtank andthe free radical initiator solution from the reactor catalyst headtankwere simultaneously fed into the reactor vessel. The feed was continuedthrough rotameters over a period of 12 hours.

g) The temperature set point of the reactor vessel was reduced over the12 hour period of addition from 140° C. to 131° C. to reduce theseverity of reflux. During this period the nitrogen flow was sufficientto blanket the reactor vessel but not so much as to displace refluxingxylene via the condenser catchpot. It was necessary to slow the nitrogenflow as the volume of the reactor vessel approached capacity during thefinal 4 hours of the monomer and catalyst feeds.

h) At the completion of the monomer and catalyst feeds the temperatureof the product was held constant at approximately 130° C. for two hoursand agitation of the product was continued during this period.

i) The product was then cooled to 100° C. This emulsifier solution hadits solids content adjusted to about 50% by weight through the additionof xylene solvent and was then used directly in the production ofemulsions. Alternatively, the majority of the xylene may be stripped offby vacuum distillation and recovered for reuse. In this case the reactorcontents would be analysed for solids and the solids content adjusted toabout 75% by weight through the addition of hydrated methanol to thereactor.

j) The product was then run-off to drums.

(ii) Production of Coupling Agent.

The preferred coupling agent is produced by a method known as anionicsolution polymerisation. This method is widely used in commercialpractice for the production of copolymers of styrene and butadiene.

In the conventional anionic solution polymerisation production process,the styrene-butadiene copolymer is usually produced in a solvent ofmixed hexanes, then precipitated by the addition of water, dried andsold in solid form. In the present emulsion production application,however, it is preferred to produce the styrene-butadiene copolymer inxylene solvent and to then recover the majority of the xylene solventand to replace it with the hydrocarbon liquid that is to form thecontinuous phase of the emulsion. The solids content of the reactionmixture is preferably maintained at about 15% by weight. This couplingagent solution may then be used directly in the production of emulsions.

Alternatively the coupling agent may be prepared by dissolving solidstyrene-butadiene copolymer in the manner described in the followingsteps used to produce a six tonne batch of coupling agent:

a) A suitably sized reactor vessel which is compatible with the couplingagent was cleaned and dried.

b) The reactor vessel was charged with:

Xylene solvent 2100.0 kg

c) With the reactor vessel cool the solvent was stirred at 60 rpm. Thefollowing was then charged into the reactor vessel through the manhole:

Styrene-butadiene copolymer solid crumb 900.0 kg

d) The manhole cover was sealed and the reactor vessel heated with thejacket temperature initially set at 120° C. As the temperature of theproduct approached 70° C. the jacket temperature was increased to 140°and the stirring rate was increased to 70 rpm.

e) The product was stirred for four hours while maintaining the producttemperature below 120° C. to avoid degradation of the copolymer. Afterthis period the product was sampled to see that it was clear and freefrom undissolved copolymer. The product was then cooled to 100° C. andthen dropped to an adjustment tank.

f) Additional solvent comprising:

xylene solvent 1500.0 kg diesel oil 1500.0 kg

were added to the product in the adjustment tank and the resultantmixture stirred until homogeneous. The product was sampled and thesolids content adjusted to 14-15% by weight.

g) The product was then run-off into drums via an in-line filter.

(iii) Production of Emulsion.

The blending facility 10 shown in FIG. 1 is designed to blend togetherdiesel oils and alcohol and/or water to form an AW/D emulsion. Theemulsion is maintained by the emulsifier and a coupling agent alreadydescribed.

Diesel oil is held in storage tank 11 and is pumped through line 12 by apump 13 to a first static in-line mixer 14. The coupling agent is ablock copolymer of styrene and butadiene dissolved in a reactionsolvent, it is stored in a stirred container 15. A metering pump 16meters the coupling agent through line 17 into the diesel oil conveyingline 12 up-stream of the first static in-line mixer 14. The first staticin-line mixer 14 serves to ensure a homogeneous solution of the couplingagent in the diesel oil.

Alcohol and/or water is stored in a tank 18. The alcohol and/or water ispumped from the tank 18 by pump 19 through line 21, including a flowcontrol valve 22, to a second static in-line mixer 23 and then to theline 12 down-stream of the first static in-line mixer 14 and up-streamof a third static in-line mixer 28. The emulsifier is a polyethyleneoxide-polystyrene copolymer dissolved in a reaction solvent (or inhydrated alcohol) and is stored in a stirred tank 24 which is maintainedat between 35 and 40° C. by heating coil 25. The emulsifier is pumped bymetering pump 26 along line 27 into line 21, which it enters down-streamof the second mixer 23. The mixer 23 serves to ensure a homogeneoussolution of the emulsifier in the alcohol and/or water. The combinedflow of line 12 is then passed through the third static in-line mixer28.

The homogeneous liquid mixture in line 12 emerging from the thirdin-line mixer 28 is passed through a fixed displacement pump 29 whichhas a pressure rise of about 15 bar. The pump 29 conveys the liquidmixture to an in-line static high shear disperser 31 where the emulsionis formed. The emulsion is then passed through a final static in-linemixer 32 and directed through line 33 to a storage tank 34.

If the installation 10 is designed to produce 50 cubic meters per hourof emulsion containing 10% by volume of hydrated ethanol then the pump13 is operated to pump the diesel oil at approximately 44 cubic metersper hour. The solution of the coupling agent is metered into the dieselat from 0.30 to 0.58 cubic meters per hour by the metering pump 16. Thehydrated ethanol flow is controlled by the flow control valve to 5 cubicmeters per hour. Metering pump 26 pumps the solution of the emulsifier,as a 50% solids solution in xylene reaction solvent, into the alcoholand/or water at a rate of from 0.42 to 0.48 cubic meters per hour.

(iv) Susceptibility of Emulsions to Stratification.

Emulsions comprising 15% by volume of hydrated ethanol, being thedispersed phase, and diesel oil, being the continuous phase, were testedfor stratification. The emulsions were stabilised with an emulsifiercomprising a polyethylene oxide-polystyrene copolymer (PEOPS) and acoupling agent comprising a polystyrene-polybutadiene copolymer (PSPB).In each case the total weight of the emulsifier and coupling agenttogether was 9 grams per liter of emulsion. The weight ratio of thePEOPS to the PSPB was varied and the effect of this change correlatedwith the propensity of the emulsion to stratify.

The propensity of the emulsions to stratify was determined by measuringthe percentage of dispersed phase that had stratified at 112 days ofundisturbed storage at ambient temperature. The results are shown inFIG. 2. It can be seen that the propensity of the emulsions to stratifyreduces significantly above a weight ratio of PEOPS to PSPB of 3:1.Similar results are obtained with total amounts of the emulsifier andcoupling agent in the range of 5 to 8 gm/l.

It will be appreciated by persons skilled in the art that numerouschanges may be made to the specific embodiments described withoutdeparting from the spirit or scope of the invention as broadlydescribed. The present embodiments are, therefore, to be considered inall respects as illustrative and not restrictive.

What is claimed is:
 1. An emulsion containing in a continuous phase ahydrocarbon liquid and in a dispersed phase alcohol and/or water in thepresence of: (a) an emulsifier being a copolymer containing at least onerelatively hydrophobic polymeric block of at least one monomer selectedfrom the group comprising styrene and ring substituted styrenes, and atleast one relatively hydrophilic polymeric block of at least one monomerselected from the group having the formula H(O—R)_(n) OH where R is analiphatic radical containing from 1 to 4 carbon atoms and n is a numberbetween 20 and 300, and (b) a coupling agent being a copolymercontaining at least one polymeric block of at least one monomer selectedfrom the group comprising styrene and ring substituted styrenes, and atleast one block being a saturated or unsaturated aliphatic hydrocarbonmoiety, the emulsifier and the coupling agent being present in theemulsion in a weight ratio of greater than 3.0:1, with the emulsifierbeing present in an amount sufficient to form micelles of the relativelyhydrophilic polymer block sufficient to contain the dispersed phase andthe coupling agent being present in an amount that is sufficient tosubstantially prevent the dispersed phase droplets from coalescing whilenot being present in a sufficiently high amount that micelles of thestyrene containing polymeric blocks of the coupling agent form in thecontinuous phase of the emulsion.
 2. An emulsion as claimed in claim 1,in which the amount of the coupling agent in the emulsion is in therange of from 0.75 to 1.5 gm/l.
 3. An emulsion as claimed in claim 2, inwhich the dispersed phase contains hydrated methanol and in which theamount of the coupling agent in the emulsion is in the range of from0.75 to 1.0 gm/l.
 4. An emulsion as claimed in claim 2, in which thedispersed phase contains hydrated ethanol and in which the amount of thecoupling agent in the emulsion is in the range of from 1.0 to 1.5 gm/l.5. An emulsion as claimed in claim 1, in which the total copolymercontent of the emulsion is in the range of from 4 to 10 gm/l.
 6. Anemulsion as claimed in claim 5, in which the dispersed phase containshydrated methanol and in which the total copolymer content of theemulsion is in the range of from 4 to 6 gm/l.
 7. An emulsion as claimedin claim 5, in which the dispersed phase contains hydrated ethanol andin which the total copolymer content of the emulsion is in the range offrom 5 to 8 gm/l.
 8. An emulsion containing in a continuous phase dieseloil and in a dispersed phase a hydrated alcohol in the presence of: (a)an emulsifier being a copolymer containing at least one relativelyhydrophobic polymeric block of styrene monomer, and at least onerelatively hydrophilic polymeric block of ethylene oxide having amolecular weight between 1,000 and 10,000, the polyethylene oxide andthe polystyrene being present in a weight ratio of from 1:0.8 to 1:1.5,and (b) a coupling agent being a copolymer containing at least onepolymeric block of styrene monomer and at least one block beingpolybutadiene, the polystyrene and the polybutadiene being present in aweight ratio of from 1:0.3 to 1:1, the emulsifier being present in anamount sufficient to form micelles of the relatively hydrophilic polymerblock sufficient to contain the dispersed phase and the coupling agentbeing present in an amount of from 0.75 to 1.5 gm/l that is sufficientto substantially prevent the dispersed phase droplets from coalescingwhile not being present in a sufficiently high amount that micelles ofthe styrene containing polymeric blocks of the coupling agent form inthe continuous phase of the emulsion, the emulsifier and the couplingagent being present in the emulsion in a weight ratio of from 3.5:1 to10:1.
 9. An emulsion as claimed in claim 1, in which the emulsifier andthe coupling agent are present in the emulsion in a weight ratio of fromat least 3.5:1 to 10:1.
 10. An emulsion as claimed in claim 1, in whichthe hydrocarbon liquid is selected from the group comprising gasolines,kerosenes, diesel oils, gas oils and fuel oils.
 11. An emulsion asclaimed in claim 1, in which the hydrocarbon liquid is a diesel oil. 12.An emulsion as claimed in claim 1, in which the dispersed phase of theemulsion comprises a hydrated alcohol which contains from 0.1 to 10% byvolume of water.
 13. An emulsion as claimed in claim 1, in which thedispersed phase of the emulsion contains a hydrated alcohol andcomprises between 10 and 30% by volume of the emulsion.
 14. An emulsionas claimed in claim 1, in which the emulsifier is a copolymer containingat least one polymeric block of at least one monomer selected from thegroup comprising styrene and ring substituted styrenes and at least onepolymeric block of at least one monomer selected from the group havingthe formula H(O—R)_(n) OH, where R is an aliphatic bivalent hydrocarbonradical containing from 1 to 4 carbon atoms and n is a number between 22and
 130. 15. An emulsion as claimed in claim 1, in which the emulsifieris a pure diblock copolymer or a reaction mixture containing principallydi-block copolymer and tri-block copolymer having two blocks of thestyrene monomer, together with some unreacted homopolymer of theH(O—R)_(n) OH monomer.
 16. An emulsion as claimed in claim 1, in whichthe emulsifier is a polyethylene oxide-polystyrene copolymer.
 17. Anemulsion as claimed in claim 16, in which the polyethylene oxide blockhas a molecular weight of between 1,000 and 10,000.
 18. An emulsion asclaimed in claim 16, in which the polyethylene oxide and the polystyreneare present in a weight ratio of 1 part of polyethylene oxide to from0.8 to 1.5 parts of polystyrene.
 19. An emulsion as claimed in claim 16,in which the emulsifier is produced by the reaction of styrene monomerwith polyethylene oxide homopolymer in the presence of a free radicalinitiator.
 20. An emulsion as claimed in claim 1, in which the couplingagent is a copolymer containing at least one polymeric block of at leastone monomer selected from the group comprising styrene and ringsubstituted styrenes and at least one polymeric block of at least onecompound selected from the group butadiene and isoprene.
 21. An emulsionas claimed in claim 1, in which the coupling agent is a pure diblockcopolymer or a tapered block copolymer.
 22. An emulsion as claimed inclaim 1, in which the coupling agent contains styrene and the aliphatichydrocarbon in the weight ratio of from 1:0.3 to 1:1.
 23. An emulsion asclaimed in claim 1, in which the coupling agent has a molecular weightof from 100,000 to 170,000.
 24. An emulsion as claimed in claim 1, inwhich styrene comprises from 50 to 77% by weight of the coupling agent.25. An emulsion as claimed in claim 24, in which the aromatic content ofthe continuous phase is less than 22% and in which styrene comprisesfrom 50 to 60% by weight of the coupling agent.
 26. An emulsion asclaimed in claim 24, in which the aromatic content of the continuousphase is more than 23% and in which styrene comprises from 60 to 70% byweight of the coupling agent.